The leaves and terminal branchlets were collected in the Dimbulah region of north eastern Queensland, Australia. The first collection (R99-218) was located 5 km north and the second collection (R99-219) 30 km west of Dimbulah.

Two chemical forms yielding 0.6% and 0.3% on a dry weight basis were found to be rich in kessane (88.8%) and alpha-pinene (16.2%), respectively.

Ten different plants of wormwood were collected in March 1997 from each one of the following four wild populations in the Spanish Pyrenees: Tallo de Aulet (prov. Huesca) and Pont de Suert, Sort and Farga de Moles (prov. Lleida). In three of the four populations studied, there was another chemotype, with 25-65% of cis-epoxyocimene and 15-50% of chrysanthenyl acetate. This chemotype, called chemotype B, was less frequent in the Pyrenees than the chemotype A, appearing only in 17% of the samples (two samples in TallO de Aulet and in Pont de Suert and three samples in Farga de Moles).

Two chemotypes were detected; a cis-epoxyocimene type (with more than 50% of this compound) which was predominant in all the populations, and a cis-epoxyocimene + chrysanthenyl acetate type (with 25-65% of cis-epoxyocimene and 15-50% of chrysanthenyl acetate). The distribution of these chemotypes had no relation with the altitude of the samples.

Seedlings of M. quinquenervia were obtained by germinating seeds collected from trees in south Florida. Plants from each chemotype were obtained from vegetative cuttings from trees whose chemotype had previously been determined by gas chromatography (GC) and gas chromatography/mass spectroscopy (GC/MS). All plants were transplanted into larger pots (11.4 L) when about 25 cm tall. These plants were fertilized with 90 g/pot Osmocote Plus 15-9-12, N-P-K (Scotts-Sierra Horticultural Products, Marysville, OH) in a slow-release 'southern' formulation . Plants were grown in a screenhouse that received rainwater and daily irrigation from overhead sprinklers for approximately 6 months at which time the plants were about 1 m tall. Three times weekly, leaves were clipped from trees and brought back to the laboratory. As O. vitiosa is a known Xush-feeder, only the silky terminal 15 cm tip leaves of each tree were collected and either used for plant quality analysis or fed to larvae.

M. quinquenervia chemotypes were distinguished by the principal terpenoids E-nerolidol and viridiflorol using gas chromatography and mass spectroscopy. Not only were the terpenoid profiles of the two chemotypes different but the viridiflorol leaves had greater toughness (1.2-fold) and reduced nitrogen (0.7-fold). When the larvae and adults were fed leaves of the E-nerolidol chemotype increased adult biomass (1.1-fold) and fecundity were found (2.6- to 4.5-fold) compared with those fed leaves of the viridiflorol chemotype. Regardless of the larval diet, when adults were fed the E-nerolidol chemotype leaves they had greater egg production compared with those adults fed the viridiflorol leaves. Moreover, adult pre-oviposition period was extended (1.5-fold) when individuals were fed the viridiflorol leaves compared with those fed the E-nerolidol leaves. By rearing the O. vitiosa weevil on the more nutritious chemotype plants these results assisted in the mass production and establishment of the M. quinquenervia biological control agent.

One hundred grams of mature leaves were collected from 2 to 10 widely spaced trees per site and sent to Sydney for analysis as soon as possible after collection. Samples usually arrived in the laboratory within 48 h of collection. The majority of the sampling was done between December 1998 and October 1999. Seasonal trends in oil yields and composition are confounded in the data on geographic variation, but these were considered minor in the context of this study.

Chemotype 1 is comprised of E-nerolidol (74-95%) and linalool (14-30%) and is found from Sydney, north along the east coast of Australia to Selection Flat, New South Wales, with an isolated occurrence near Maryborough, Queensland. Two divisions occur in this chemotype which are based on the presence or absence of significant proportions of linalool (14-40%). Chemotype 2 contains 1,8-cineole (10-75%), viridiflorol (13-66%), alpha-terpineol (0.5-14%) and beta-caryophyllene (0.5-28%) in varying proportions and order of dominance in the oils. It is found throughout the distribution of the species, from Sydney to Papua New Guinea and New Caledonia. Within chemotype 2 there appears to be a continuous spread of oil composition without formation of any further discrete divisions as in chemotype 1. Analyses have shown that M. quinquenervia trees that occur at latitudes south of 25d S have high oil yields (1-3% w/w%, fresh leaves) and comprise chemotypes 1 and 2. North of 25d S, however, chemotype 1 does not occur and oil yields amongst the Australian populations are uniformly low (0.1-0.2%).